Category: Time series and analysis
NDVI
NDVI is a vegetation index that uses red and near-infrared reflectance to approximate vegetation greenness and vigor.
Also known as: Normalized Difference Vegetation Index
Expanded definition
NDVI stands for Normalized Difference Vegetation Index and is computed as (NIR - Red) / (NIR + Red). Healthy green vegetation typically reflects more NIR and less red, producing higher NDVI values.
NDVI is widely used because it is simple and correlates with vegetation density and photosynthetic activity in many conditions. It can saturate in dense canopies and it is sensitive to soil background, atmosphere, and shadows.
NDVI works best when computed from consistent reflectance products (often surface reflectance) with good cloud and shadow masking. Comparing NDVI across sensors also requires attention to band definitions and calibration.
Related terms
Band
A band is a single spectral channel in an image, measuring energy within a specific wavelength range.
Reflectance
Reflectance is the fraction of incoming light that a surface reflects, commonly used for analysis and comparison.
Surface Reflectance (BOA)
Surface reflectance estimates what reflectance would be at the ground after removing atmospheric effects.
Cloud Mask
A cloud mask labels pixels likely affected by clouds so they can be excluded or handled differently.